This invention relates to apparatus for supplying molten metal to a die cast machine, and more particularly apparatus for supplying molten metal by utilizing an electromagnetic pump.
An electromagnetic pump has been used for supplying molten metal to the injection sleeve of a die cast machine from a furnace constructed to maintain the temperature of the molten metal. Such prior art apparatus will firstly be described with reference to FIGS. 3 and 4.
In these figures, a furnace for maintaining the temperature of molten metal is designated by a reference numeral 1 and a pot 3 containing the molten metal 2 is disposed in the furnace 1 with a suitable spacing therebetween.
A molten metal supply pipe 4 is connected to the side wall of the pot 3 so as to connect an injection sleeve 45 to the pot 3.
The molten metal supply pipe 4 is constituted by a duct 4a extending through the side wall of the furnace 1 and opens into the pot 3, and a molten metal supply pipe 4b. A magnetic core 6 is inserted into duct 4a through the outer end thereof. A packing member 7 is interposed between the enlarged head of core 6 and the outer end of duct 4a so as to prevent leakage of the molten metal.
An inverted L shaped molten metal supply pipe 4b vertically extends from the outer end of duct 4a and the upper end of pipe 4b is connected to an injection sleeve 45.
An electromagnetic coil 5 is mounted about the duct 4a, the electromagnetic coil 5 constituting an electromagnetic pump together with the magnetic core 6. The electromagnetic pump operates in a manner well known in the art for pumping the molten metal in the pot 3 to the injection sleeve 45.
With the prior art molten metal supply apparatus of the type described above, in order to exchange the magnetic core 6, after discharging the molten metal 2 in pot 3 it is necessary to withdraw the core 6 from the duct 4a. This not only requires a certain time for exchanging the core but also requires to provide an operating space of a volume necessary to withdraw the core. At the same time it is also necessary to exchange the packing member 7.
On the other hand, in an electromagnetic pump utilized to pump molten metal, the inner surface of pipe 4a is corroded by the molten metal so that in the prior art design the pipe 4a was made of such ceramics as silicon nitride or alumina which is nonmagnetic and resistant to molten metal.
However, a pipe or duct made of ceramic is liable to be broken by a heat shock or a mechanical shock. To obviate this problem it has been considered to apply the ceramic to the inner surface of the duct by flame coating method or melt coating method. However such method is difficult where the inner diameter of the duct is small.